There is an button to generate a bill from an inbound shipment record. Any ideas how I could trigger this process in code?

SuiteScript Supported Records shows transform action is not supported for Inbound Shipments Just as a FYI/PSA

Yes. But somehow inbound shipments work differently than the rest of Netsuite's API. For example, to create an

Ownership Transfer

from a Inbound Shipment, you don't transform it. Rather you load and save a record.Type.BULK_OWNERSHIP_TRANSFER with the same Id as the inbound shipment. I only knew that from the sample code in the Help center. I didn't actually see that as the documented way to do that. I tried the same method for the

billinboundshipment

which is the record in the url when generating the bill in the UI, but there is no such record type when I try to do it in code